1. Field of Invention
The present invention relates to switches for controlling electric circuits, and, more particularly, for controlling circuits in which high current is present. Moreover, the switch of the present invention is activated by pulling on an actuator, and deactivated by pushing the same.
2. Description of the Prior Art
One general type of switch used for controlling electric circuits includes an electromagnet. When energized, the electromagnet moves an armature that in turn closes or opens one or more electrical contacts. The energized electromagnet then holds the armature in such a position that the contacts remain closed or open. When the electromagnet is deenergized, the armature, and in turn the contacts, return to their initial positions.
This type of switch is particularly useful in circuits in which high current is present. Whenever the contacts in any type of switch in a high-current circuit are closed or opened, arcing results as the contact members approach or move away from each other. This arcing can lead to the contacts becoming welded together. It also causes erosion of the contact material and greatly shortens contact life. In some switches where the contacts are manually closed or opened, the operator is apt to close or open them slowly. This results in a long period for arcing and high probability of contact erosion or of welding the contacts. In a switch where the contacts are closed or opened by an electromagnet, however, the contacts move quickly. The length of time during which arcing can occur is greatly reduced, and the contact erosion and the possibility of welding the contacts is therefore significantly lowered.
The standard relay is an example of the type of switch discussed above. In a relay, the electromagnet is energized and deenergized by an electrical control means remote from the relay. While useful in high-current circuits, in some applications a relay has several disadvantages. The remote energizing control increases the bulk and complexity of the switching device. Additionally, in situations where it is necessary to keep the switch air and watertight, a remote energizing control and the associated wiring conduits and connection points significantly increase the opportunities for leakage. Moreover, in the event of "tacking," or sticking, of the contacts upon attempting to open them, the operator has no real means for freeing the contacts and controlling the circuit short of disassembling the switch.
U.S. Pat. No. 3,622,925 discloses another example of a switch of this general type. A switch is shown wherein a push-button type actuator is used to close a pair of normally-open contacts and thereby energize an electromagnet. The electromagnet moves an armature that engages the same contacts, holding them closed. Although the switch reduces the bulk and leakage potential of the relay, it is a starting switch only. A circuit activated by the switch cannot be deactivated by the same switch. Further, since the contacts held closed by the actuator are initially closed manually, such a switch will not reduce the possibility for welding of the contacts in high current applications. Moreover, the switch provides no means for separating the contacts in the event of "tacking."
U.S. Pat. No. 3,848,205 discloses yet another example of the general type of switch. A switch for controlling an electric motor is shown wherein an electromagnet is connected across a pair of normally-closed contacts. An actuator and a projection are mounted to an armature. Upon movement of the actuator, the armature, and in turn the projection, are moved so that the projection engages and opens the contacts. The electromagnet is then energized and holds the armature causing the projection to hold the contacts open. By energizing the electromagnet, current through the motor is reduced such that the motor will stop. While this switch also reduces the bulk and leakage potential of the relay, it cannot restart the stopped motor. Moreover, such a switch does not completely deactivate the circuit.